Run manta-pay randomized tests in a loop in CI

[ghzlatarev]

MantaPay tests are currently randomized to a degree, which is great, however sometimes it could take a few tries to catch bugs, depending on what kind of random values are used in each instance. That's why we should run these tests say 2 - 5 time, however there's a tradeoff that this will slow down the CI, which should be balanced. This could be a good first issue for someone as it is just changes in CI and measurements.